Rotor wedges and methods of making rotor wedges

ABSTRACT

A wedge for a wound rotor includes a wedge body. The wedge body has a first layer and one or more second layers interfused with one another to provide structural support and limit resistive heating of the wedge from current flow within the wedge body by windings spaced apart by the rotor wedge. Generator rotors and methods of making generator rotors are also described.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a divisional of U.S. patent application Ser. No. 15/721,011filed Sep. 29, 2017 the contents of which are incorporated herein byreference in their entirety.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present disclosure relates to wound rotors, and more particularlyrotor wedges for wound rotors in synchronous machines like generators.

2. Description of Related Art

Synchronous machines with wound rotors, such as motor and generators,are used on aircraft to convert mechanical power to device and generateelectrical power. Electric current applied to wound rotor typicallygenerates a magnetic field. In the case of electric motors the rotormagnetic field interacts with a stator magnetic field to generatemechanical power. In the case of electric generators mechanical rotationapplied to the rotor rotates the rotor magnetic field relative to thestator to induce a flow of electric current in the stator windings.

Rotors in synchronous machines require structure sufficiently robust towithstand the forces associated with rotation. In some synchronousmachines the rotor is constructed with wedges. The wedges are generallyseated within the rotor about the rotor periphery and betweencircumferentially adjacent windings. The wedges are typicallyconstructed of material like aluminum or aluminum alloy. Such rotorwedges constructed of aluminum or aluminum alloy typically provide astrong and lightweight construction that is inexpensive and lightweight.Such rotor wedges readily dissipate heat due to the electricalconductivity of aluminum and aluminum alloys.

Such conventional methods and systems have generally been consideredsatisfactory for their intended purpose. However, there is still a needin the art for improved rotor wedges, rotor arrangements, and methods ofmaking rotor wedges for wound rotors. The present disclosure provides asolution for this need.

SUMMARY OF THE INVENTION

A wedge for a wound rotor includes a wedge body. The wedge body includesa plurality of layers interfused with one another to provide structuralsupport and limit resistive heating of the wedge from current flowwithin the wedge body by windings spaced apart by the rotor wedge. Incertain embodiments, the wedge body can include titanium or a titaniumalloy. The wedge body can have a longitudinal profile with a generallypolygonal or triangular shape, a stator face and an opposed apex, andfirst and second winding faces. The first and second winding faces canextend on laterally opposite sides of the wedge body and span the apexand the stator face of wedge body.

In accordance with certain embodiments, the wedge body can include oneor more cooling channels. The one or more cooling channels can bedefined within the stator face of the wedge body. The cooling channelscan extend longitudinally along a length of the wedge body. The wedgebody can include one or more channel. The channel can extend betweenlongitudinally opposite ends of the wedge body. The channel can bearranged centrally between the apex and the stator face of the wedgebody.

In accordance with further embodiments, the channel can be a majorchannel. The wedge body can include a pair of minor channels. The majorchannel can be arranged between the apex and the stator face of thewedge body. A first of the minor channels can be arranged between themajor channel and the first winding face of the wedge body. A second ofthe minor channels can be arranged between the major channel and thesecond winding face of the wedge body.

It is contemplated that, in accordance with certain embodiments, thewedge can include a heat transfer plate. The heat transfer plate can becoupled to stator face of the wedge body. The heat transfer plate canextend along the longitudinal length of the wedge body. The heattransfer plate can include a material with thermal conductivity that ishigher than the material forming the wedge body. The heat transfer platecan include aluminum or an aluminum alloy

It is also contemplated that, in accordance with certain embodiments, aninsulating layer can be deposited over the winding faces and the apex ofthe wedge body. The insulating layer can extend contiguously betweenopposite longitudinal ends of the wedge body. The insulating layer caninclude a polymeric material. A heat sink can be fixed to a longitudinalend of the wedge body. The heat sink can include a finned body. The heatsink can include a material having higher thermal conductivity than thethermal conductivity of the material forming the wedge body. The heatsink can include aluminum or an aluminum alloy.

A wound rotor includes a rotor body, first and second windings, and awedge as described above. The rotor body is supported for rotation abouta rotation axis and has a winding slot. The first and second windingsare arranged in the winding slot, the second winding slot beingcircumferentially offset form the first winding. The wedge is seated thewinding with the first winding face abutting the first winding, thesecond winding face abutting the second winding, and the wedge bodyelectrically separating the first winding from the second winding.

In certain embodiments the second winding can be thermally isolated fromthe first winding by the wedge body. An insulating layer can bedeposited over the first winding face, the second winding face, and theapex. The insulating body can extend continuously between longitudinallyopposite ends of the wedge body. The wedge body can include titanium ora titanium alloy.

In accordance with certain embodiments, the wedge body can have a majorchannel and first and second minor channels. The major and minor channelcan extend between longitudinally opposite ends of the wedge body. Aheat transfer plate can be coupled to the stator face of the wedge bodyradially outward of the apex of the wedge body. The heat transfer platecan include a material with thermal conductivity that is higher thanthermal conductivity of the material forming wedge body. The heattransfer plate can include aluminum or an aluminum alloy.

A method of making a wedge for a wound rotor includes fusing first andone or more second layers to form a wedge body as described above.Fusing the first and second layers can include fusing a particulateincluding titanium in an additive manufacturing apparatus. The methodcan include depositing an insulating layer over the first and secondwinding faces and the apex of the wedge body. The method can include oneor more of (a) coupling a heat transfer plate to the stator face of thewedge body, (b) coupling a heat sink to a first longitudinal end of thewedge body, and (c) coupling a heat sink to a second longitudinal end ofthe wedge body.

These and other features of the systems and methods of the subjectdisclosure will become more readily apparent to those skilled in the artfrom the following detailed description of the preferred embodimentstaken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

So that those skilled in the art to which the subject disclosureappertains will readily understand how to make and use the devices andmethods of the subject disclosure without undue experimentation,embodiments thereof will be described in detail herein below withreference to certain figures, wherein:

FIG. 1 is a schematic view of an exemplary embodiment of an aircraftelectrical system constructed in accordance with the present disclosure,showing a generator with a wound rotor;

FIG. 2 is perspective view of the wound rotor of FIG. 1, showing a rotorbody with rotor wedges and windings arranged about the radial peripheryof the rotor body;

FIG. 3 is a perspective view of the rotor wedge of FIG. 2, showing awedge body having opposed longitudinal ends and a longitudinal profile;

FIG. 4 is a longitudinal end view of the rotor wedge of FIG. 2, showingthe longitudinal profile and an insulating layer deposited over windingfaces of the wedge body;

FIG. 5 is a longitudinal end view of the rotor wedge of FIG. 2, showinga coolant conduit defined in rotor wedge stator face and a heat transferplate coupled to the stator face;

FIG. 6 is a perspective view of the rotor wedge of FIG. 2, showing heatsinks coupled to the rotor wedge at longitudinally opposite ends of thewedge body; and

FIGS. 7A-7E show a method of making a wound rotor for a liquid cooledsynchronous machine generator, each figure schematically showing anoperation of the method.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made to the drawings wherein like referencenumerals identify similar structural features or aspects of the subjectdisclosure. For purposes of explanation and illustration, and notlimitation, a partial view of an exemplary embodiment of a wedge for awound rotor 100 in accordance with the disclosure is shown in FIG. 2 andis designated generally by reference character 100. Other embodiments ofrotor wedges, wound rotors and methods of making rotor wedges inaccordance with the disclosure, or aspects thereof, are provided inFIGS. 1 and 3-7, as will be described. The systems and methods describedherein can be used wound rotors, such as in generators in aircraftelectrical systems, though the present disclosure is not limited togenerators or to aircraft electrical systems in general.

Referring to FIG. 1, an aircraft electrical system 10 is shown. Aircraftelectrical system 10 includes a generator 104, a power bus 14, and aplurality of power consuming devices 16. An engine 18, e.g., an aircraftmain engine or an auxiliary power unit, is operably connected to thegenerator 12 and arranged to provide mechanical rotation R of a woundrotor 102 (shown in FIG. 2) of generator 12. Generator 12 iselectrically connected to the plurality of power consuming devices 16 bypower bus 14 and is arranged to provide electrical power P to theplurality of power consuming devices 16 through power bus 14 usingmechanical rotation R received from engine 18. It is contemplated thatgenerator 12 be a synchronous machine electrical generator that, incertain embodiments, employs a liquid coolant 405 (shown in FIG. 6) toremove heat from wound rotor 102. Although described herein as a woundrotor for a generator, it is to be understood and appreciated that othertypes of electrical machines can also benefit from the presentdisclosure, such as electric motors and starter/generators by way ofnon-limiting example.

With reference to FIG. 2, wound rotor 102 is shown. Wound rotor 102 issupported for rotation about a rotation axis 106 and includes a corebody 108, a first winding 110, a second winding 112, and rotor wedge100. Core body 108 is constructed from an electrical steel material 114and has a radially outer periphery 116 and a plurality of slots 118.Slots 118 are defined within periphery 116 and extend longitudinallyalong an axial length of core body 108.

First winding 110 and second winding 112 are seated within a common slot118. Rotor wedge 100 is circumferentially interposed between firstwinding 110 and second winding 112 to retain first winding 110 andsecond winding 112 within core body 108 during rotation of wound rotor102 about rotation axis 106. Collars 121 are arranged at longitudinallyopposite ends of core body 108 radially overlap rotor wedge 100. In theillustrated exemplary embodiment wound rotor 100 has four windings andfour rotor wedges. As will be appreciated by those of skill in the artin view of the present disclosure wound rotor 102 can have more thanfour windings or fewer than four windings, as suitable for an intendedapplication. As will also be appreciated by those of skill in the art inview of the present disclosure, wound rotor 102 can have more than fourrotor wedges or fewer than four rotor wedges, as suitable for anintended application.

With reference to FIG. 3, rotor wedge 100 is shown. Rotor wedge 100 hasa wedge body 122 a plurality of layers, e.g., a first layer 146 (shownin FIG. 7A) and one or more second layer 148 (shown in FIG. 7A),interfused with one another to provide structural support and limitresistive heating of windings spaced apart by wedge body 122. In theillustrated exemplary embodiment wedge body 122 has a longitudinalprofile 124. Longitudinal profile 124 has a generally polygonal shapebounded by a stator face 126, the exemplary polygonal shape illustratedin FIG. 3 being triangular and having an apex 128, a first winding face130, and a second winding face 132. Stator face 126 has a planar shapeor an arcuate shape, as suitable for an intended application.

First winding face 130 and second winding face 132 extend longitudinallyon laterally opposite sides of wedge body 122. Apex 128 extendslongitudinally along the length of wedge body 122 and bounds firstwinding face 130 and second winding face 132. It is contemplated thatwedge body 122 be constructed from a wedge material 134 that haselectrical resistivity higher than that of aluminum such that rotorwedge 100 generates relatively little (or no) heat. In certainembodiments wedge material 134 includes titanium or a titanium alloy,thereby providing a rotor wedge that is strong, light, and does notgenerate heat from current flow induced by magnetic fields in proximityto rotor wedge 100, e.g., to provide structural support to and limitresistive heating of the wedge caused by current flow within the wedgebody by windings spaced apart by the rotor wedge. As will be appreciatedby those of skill in the art in view of the present disclosure otherpolygonal shapes of longitudinal profile are possible within the scopeof the present disclosure.

One challenge to fabricating rotor wedges using materials like titaniumand titanium alloys is the relatively high cost of titanium to costusing traditional subtractive manufacturing techniques. To overcome thisproblem wedge body 122 is constructed using an additive manufacturingtechnique where a plurality of layers, e.g., a first layer 146 (shown inFIG. 7A) and a second layer 148 (shown in FIG. 7A), are fused to oneanother. An example of a suitable additive manufacturing technique israpid plasma deposition. Constructing wedge body 122 with a plurality oflayers can reduce the cost of wedge body 122. In certain embodiments thecost of manufacturing wedge body 122 from titanium or titanium alloy ison the order of 25% to 50% that of fabricating wedge body 122 using asubtractive manufacturing technique. Use of an additive manufacturingtechnique also allows for incorporating of features in wedge body 122that could otherwise be prohibitively expensive using subtractivemanufacturing techniques, such as voids and/or hollows within wedge body122.

For example, in the illustrated exemplary embodiment wedge body 122 hasa plurality of channels defined within its interior for reducing theweight of wedge body 122. In this respect wedge body 122 has a majorchannel 136, a first minor channel 138, and a second minor channel 140.Major channel 136 extends longitudinally along the length of wedge body122 between a first longitudinal end 142 and a longitudinally oppositesecond longitudinal end 144. Major channel 136 is arranged radiallyrelative to rotation axis 106 (shown in FIG. 2) between apex 128 andstator face 126.

First minor channel 138 extends longitudinally along the length of wedgebody 122 between first longitudinal end 142 and second longitudinal end144, and is arranged between major channel 136 and first winding face130. Second minor channel 140 also extends longitudinally along thelength of wedge body 122 between first longitudinal end 142 and secondlongitudinal end 144, and is arranged between major channel 136 andsecond winding face 132. Although three weight reduction channels areshown in the illustrated exemplary embodiment, those of skill in the artwill readily appreciate in view of the present disclosure that wedgebody can have fewer than three channels or more than three channels, assuitable for an intended application. As will also be appreciated bythose of skill in the art in view of the present disclosure, channelshaving shapes other than circular can also be defined within wedge body122, as suitable for an intended application.

With reference to FIG. 4, a rotor wedge 200 is shown. Rotor wedge 200 issimilar to rotor wedge 100 (shown in FIG. 2) and additionally includesan insulating layer 201. Insulating layer 201 includes a polymericmaterial 203 deposited over surfaces of wedge body 222 in abutting firstwinding 110 (shown in FIG. 2) and second winding 112 (shown in FIG. 2).In the illustrated exemplary embodiment insulating layer 201 isdeposited over first winding face 230, apex 228, and second winding face232 and along the longitudinal length of wedge body 222. Insulatinglayer 201 is not disposed over stator face 226.

It is contemplated that polymeric material have electrical insulatingproperties similar to polyimide, e.g., Kapton®, available from the E. I.du Pont de Nemours and Company Corporation of Wilmington, Del. Beingdeposited on first winding face 130 and second winding face 132,polymeric material 203 eliminates the need to incorporate insulatingsheets that otherwise can be required in wound rotors between windingsand rotor wedges, simplifying assembly wound rotor 202. Examples ofsuitable polymeric materials include polyether ether ketone (PEEK),available from Victrex PLC of Lancashire, United Kingdom.

With reference to FIG. 5, a rotor wedge 300 is shown. Rotor wedge 300 issimilar to rotor wedge 100 (shown in FIG. 2) and additionally includes aheat transfer plate 301. Heat transfer plate 301 is coupled to statorface 326 of wedge body 322, extends, longitudinally along the length ofwedge body 322, and includes a plate material 303. Plate material 303has thermal conductivity that is higher than the thermal conductivity ofwedge material 334. This allows for heat generated an air gap 305defined between rotor wedge 300 and a stator 307 to transfer into heattransfer plate 301, and therethrough to longitudinally opposite ends ofrotor wedge 300 for removal. It is contemplated that plate material 303have electrical conductivity and/or magnetic permeability that isgreater than that of wedge material 334. In certain embodiments platematerial 303 includes aluminum or an aluminum alloy. In accordance withcertain embodiments wedge material 334 can include titanium or atitanium alloy directly coupled to heat transfer plate 301 at statorface 326.

As also shown in FIG. 5, rotor wedge 300 can have one or more coolantconduit 309 defined within wedge body 322. The one or more coolantconduit 309 is arranged to convey a coolant fluid longitudinally alongthe length of rotor wedge 300 to remove heat generated by windage acrossheat transfer plate 301. In the illustrated exemplary embodiment the oneor more coolant conduit 309 is defined within stator face 326 and isbounded by heat transfer plate 301 at a radially outer portion of wedgebody 322. As will be appreciated by those of skill in the art, arrangingthe one or more coolant conduit 309 allows for removal of heat from heattransfer plate 301 directly, without the need to communicate the heatthrough wedge material 334.

With reference to FIG. 6, a rotor wedge 400 is shown. Rotor wedge 400 issimilar to rotor wedge 100 (shown in FIG. 2) and additional includes aheat sink 401. Heat sink 401 has a plurality of fins 403 arranged toreceive a coolant flow 405 to transfer heat from rotor wedge 400 and iscoupled to first longitudinal end 442. It is contemplated that heat sink401 be constructed from a heat sink material 407 having thermalconductivity that is higher than the thermal conductivity of wedgematerial 434 forming wedge body 422. In the illustrated exemplaryembodiment heat sink 401 is a first heat sink and rotor wedge 400includes a second heat sink 409. Second heat sink 409 is coupled tosecond longitudinal end 444 and on an end of wedge body 422 oppositefirst heat sink 401. In accordance with certain embodiments, a heattransfer plate 411 can couple first heat sink 401 to second heat sink409, first heat sink 401 and second heat sink 409 in turn both beingcoupled to wedge body 422 through heat transfer plate 411.

Referring now to FIGS. 7A-7E, a method of making a rotor wedge for woundrotor is shown. As shown in FIG. 7A, method includes fusing 510 a firstlayer 146 to a second layer 148 to form wedge body 122. It iscontemplated that first layer 146 be proximate to first longitudinal end142, second layer 148 be proximate to second longitudinal end 144 andarranged on a side of first layer 146 opposite first longitudinal end142, and that successive layers thereafter be fused to second layer 148.Via an additive manufacturing technique, wedge body 122 is constructedlayerwise in the longitudinal direction. Each layer can include titaniumor titanium alloy 504 fused using an additive manufacturing technique.Examples of suitable additive manufacturing techniques include rapidplasma deposition (RPD) process tool 502. Exemplary RPD processesinclude those employing RPD process tools such as the MERKE IV RPDworkstation, available from Norsk Titanium AS of Honefoss, Norway.

Once wedge body 122 is formed heat transfer plate 303 can be coupled tostator face 126 of wedge body 122 in a coupling operation 520, as shownin FIG. 7B. Coupling can be accomplished, for example, utilizing afriction stir welding operation 522 coupling the aluminum forming heattransfer plate 303 to the titanium forming wedge body 122. Although afriction stir welding operation is shown it is to be understood andappreciated that other welding techniques may also be employed.

Insulating layer 201 is then deposited in a deposition operation 530over wedge body 122, as shown in FIG. 7C. Deposition of insulating layer201 can be through a VICOTE™ deposition process tool 532 such as thoseavailable from Victrex PLC of Lancashire, United Kingdom. It iscontemplated that insulating layer be deposited over first winding face130, second winding face 132, and apex 128 of wedge body 122. As will beappreciated by those of skill in the art in view of the presentdisclosure, performing deposition operation 530 subsequent to couplingoperation 520 prevents the heat associated with welding operation 522from disturbing insulating layer 201.

First heat sink 401 and second heat sink 409 can be coupled tolongitudinally opposite first end 442 and second end 444 in a heat sinkassembly operation 540 as shown in FIG. 7D. Heat sink operation 540 canoccur prior to deposition operation 530 or after deposition operation530, as operationally suitable. Once assembly of rotor wedge 100 iscomplete rotor wedge 100 can be seated in core body 108 within commonslot 118 and between first winding 110 and second winding 112 in a woundrotor assembly operation 550, as shown in FIG. 7E.

The methods and systems of the present disclosure, as described aboveand shown in the drawings, provide for rotor wedges with superiorproperties including good structural strength, relatively low heatgeneration, and good heat transfer capability for removing heatgenerated from windage losses. In certain embodiments, wedges describedherein have integrated heat conduction structures, simplifying assemblyof generator rotors employing the wedges. In accordance with certainembodiments, wedges described herein have integrated insulation,simplifying assembly of generator rotors employing the wedges. While theapparatus and methods of the subject disclosure have been shown anddescribed with reference to preferred embodiments, those skilled in theart will readily appreciate that change and/or modifications may be madethereto without departing from the scope of the subject disclosure.

What is claimed is:
 1. A method a making a rotor wedge for a woundrotor, comprising fusing a first layer and one or more second layers toform a wedge body.
 2. The method as recited in claim 1, wherein fusingthe first layer and the one or more second layers includes defining awedge body having a longitudinal profile with a triangular shape, astator face and an opposed apex, and first and second winding facesspanning the apex and the stator face on laterally opposite sides ofwedge body wherein fusing the first and second layers includes fusing aparticulate including titanium in an additive manufacturing apparatus.3. The method as recited in claim 2, further comprising depositing aninsulating layer over the first and second winding faces and the apex ofthe wedge body.
 4. The method as recited in claim 3, further comprisingcoupling a heat transfer plate to the stator face of the wedge body. 5.The method as recited in claim 3, further comprising coupling a heatsink to a first longitudinal end of the wedge body.
 6. The method asrecited in claim 3, further comprising coupling a heat sink to a secondlongitudinal end of the wedge body.
 7. The method as recited in claim 1,wherein the wedge body comprises titanium or titanium alloy.
 8. Themethod as recited in claim 1, further comprising coupling a heattransfer plate to a stator face of the wedge body, extending along alongitudinal length of the wedge body.
 9. The method as recited in claim8, wherein the heat transfer plate includes a material having higherthermal conductivity than a material forming the wedge body.
 10. Themethod as recited in claim 8, wherein the heat transfer plate includesaluminum or an aluminum alloy.
 11. The method as recited in claim 1,wherein the wedge body has at least one channel extending betweenlongitudinally opposite ends of the wedge body.
 12. The method asrecited in claim 11, wherein the wedge body has a major channel and apair of minor channels, the major channel arranged laterally between theapex and the stator face of the wedge body, a first of the minorchannels arranged laterally between the major channel and the firstwinding face, a second of the minor channels arranged laterally betweenthe major channel and the second winding face of the wedge body.
 13. Themethod as recited in claim 1, wherein the wedge body includes one ormore cooling channels defined within the stator face and extendinglongitudinally along the wedge body.
 14. The method as recited in claim1, further comprising depositing an insulating layer over the windingfaces and the apex of the wedge body, wherein the insulating layerextends contiguously between opposite longitudinal ends of the wedgebody.
 15. The method as recited in claim 14, wherein the insulatinglayer comprises a polymeric material.
 16. The method as recited in claim1, further comprising fixing a heat sink to a longitudinally end of thewedge body.
 17. The method as recited in claim 16, wherein the heat sinkincludes a material having higher thermal conductivity than a materialforming the wedge body.
 18. The method as recited in claim 16, whereinthe heat sink includes aluminum or aluminum alloy.
 19. The method asrecited in claim 16, wherein the heat sink includes a finned bodylongitudinally spaced apart from the wedge body.